chore(server): remove useless client allowGuestDemoWorkspace config (#12988)

#### PR Dependency Tree


* **PR #12988** 👈

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[Charcoal](https://github.com/danerwilliams/charcoal)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **Chores**
* Removed the configuration option that allowed guests to access demo
workspaces. This affects related settings in the system configuration
and admin interface.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/frontend/admin/src/config.json

@@ -211,10 +211,6 @@
     "versionControl.requiredVersion": {
       "type": "String",
       "desc": "Allowed version range of the app that allowed to access the server. Requires 'client/versionControl.enabled' to be true to take effect."
-    },
-    "allowGuestDemoWorkspace": {
-      "type": "Boolean",
-      "desc": "Allow guests to access demo workspace."
     }
   },
   "captcha": {